(a) Field of the Invention
The present invention relates to a wide-field eyepiece with a long eyepoint distance.
(b) Description of the Prior Art
Up to the present, it is considered that the optimum eyepoint distance of microscope eyepieces is 14 to 15 mm. For example, the eyepiece disclosed in Japanese published examined patent application No. 41508/71 is known as an eyepiece comparatively resembling the eyepiece according to the present invention. The eyepoint distance of said eyepiece is 14.6 mm. However, for a person who wears a pair of glasses, the distance from the eyepiece to his eye is larger than the distance from the lens of his glasses to his eye. Therefore, when using an eyepiece with the above-mentioned eyepoint distance, such inconvenience occurs for some persons that he cannot bring his eye properly to the position of eyepoint of the eyepiece. Besides, the above-mentioned known eyepiece has such disadvantage that lateral chromatic aberration of the lens system as a whole is overcorrected when it is combined with a microscope objective. Moreover, as the above-mentioned eyepiece has large spherical aberration of pupil, it has such disadvantage that eclipse of field occurs when the position of observer's eye is deviated forward or backward from the proper eyepoint position of the eyepiece though such eclipse of field does not occur as far as the observer puts his eye properly in the eyepoint position of the eyepiece.